Process and apparatus for coating objects with powdery substances

ABSTRACT

A powder spraying apparatus comprises a finishing container and a spraying system attached thereto. The spraying system comprises a nozzle portion and a connector portion which communicates the nozzle with the finishing container. The finishing container and the connector portion each have an independently controlled supply of compressed air for keeping powder particles in a fluidized, or suspended, state to prevent the particles from lumping together. The nozzle is operated by an additional supply of compressed air which creates a suction force in a manner allowing the nozzle to aspirate powder from the finishing container. By switching off the supply of compressed air to the connector portion just prior to switching off the nozzle air, the powder within the connector portion will lump, thus preventing an undesirable discharge through the nozzle under the influence of residual pressure in the finishing container. An attachment is provided for the nozzle which serves to change the shape of fluid flow therefrom and which has air flow means for preventing the particles from lumping up therein.

United States Patent 1 Gebhardt et al.

both of Wiler Zum Stein, all of Germany [73] Assignee: Firma Ernst Mueller K.G., Hofen near Winnenden, Germany [22] Filed: April2l, 1971 [21] Appl, No.: 135,868

[30] Foreign Application Priority Data April 24, 1970 Germany ..P 20 20 055.9

[52] US. Cl. ..239/8, 239/427.3, 239/428 [51] Int. Cl. ..A0ln 17/02, A62c 1/12 [58] Field of Search ..239/8, 427, 427.3, 428, 429, 239/430, 431, 433, 589; 117/16; 302/53 [56] References Cited UNITED STATES PATENTS 1,781,603 11/1930 Schori ..239/428 3,269,428 8/1966 Stockel et al.

3,307,596 3/1967 Stockeletal. .::..302/s3x [4 1 Jan. 9, 1973 Primary Examiner-M. Henson Wood, Jr. Assistant Examiner--Edwin D. Grant Attorney-Burns, Doane, Swecker & Mathis [57] ABSTRACT A powder spraying apparatus comprises a finishing container and a spraying system attached thereto. The spraying system comprises a nozzle portion and a connector portion which communicates the nozzle with the finishing container. The finishing container and the connector portion each have an independently controlled supply of compressed air for keeping powder particles in a fluidized, or suspended, state to prevent the particles from lumping together. The nozzle is operated by an additional supply of compressed air which creates a suction force in a manner allowing the nozzle to aspirate powder from the finishing container. By switching off the supply of compressed air to the connector portion just prior to switching off the nozzle air, the powder within the connector portion will lump, thus preventing an undesirable discharge through the nozzle under the influence of residual pressure in the finishing container. An attachment is provided for the nozzle which serves to change the shape of fluid flow therefrom and which has air flow means for preventing the particles from lumping up therein.

23 Claims, 6 Drawing Figures PATENTED JAN 9 I875 SHEET 1 0F 5 FIG.1

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PAIENIEDm 9197a Q 3.709434 sum 5 or 5 PROCESS AND APPARATUS FOR COATING OBJECTS WITH POWDERY SUBSTANCES BACKGROUND OF THE INVENTION The invention relates to a process and a device for electrostatically coating objects with powdery substances, whereby the powder is conducted from a supply container via pipe lines to at least one compressed air operated spray gun in which it is atomized, or diffused.

Such a process and device may be used for automatically providing mass produced objects, for example parts of a car body, refrigerator housings,etc., moving on an assembly line, with layers of paint, lacquer or primer.

In most instances, automatic spray installations are built in such a way that objects to be coated are attached to an endless conveying chain which passes through a spraying compartment in which several spray guns are rigidly or automatically movably disposed. The spray guns are fed from a common supply container, disposed outside the spraying compartment, via feed pipes. The development of theseautomatic spray installations was made originally for the purpose of spraying liquid coating materials. With the development of powdery coating materials, especially powdery paints or plastic enamels, etc., it became desirable to create automatic spraying installations for the spraying of powder. In this case, however, considerable difficulties arose, particularly concerning the conveyance of the powdery coating material from the supply container to the spray guns or the spraying positions.

In the case of supplying liquid coating materials, it was customary, for example, to dispose the supply container above the spraying compartment, whereby the coating material flowed by itself, as a result of the effect of gravity, to the below-positioned spray guns. The quantities of fed-in material could be precisely controlled for every gun in a simple manner by means of valves located in the feed pipes.

The method used for liquid coatings, however, is not practical fprspraying powdery coating materials. The powdery coating materials are distinguished by the fact that they are not very fluid and rather would have to be called self-locking. In other words, the powder, as it passes through pipe lines, shows a strong inclination to bake or lump together and to plug up the pipes. This impedes a precise regulation of thepowder to be supplied, and in most cases soon leads to a complete interruption of the powder feed.

A powder spraying installation has been known in which the attempt was made to overcome the pluggingup problem by arranging a jet pump at the outlet of the supply container to blow the powder at a relatively high speed through the pipe lines to the individual spray guns. Apart from the high consumption of air resulting in this case, the conveying problem was not solved satisfactorily. As a result of the high speed of the powder particles in the pipe lines, a heating of the powder takes place as a result of friction, especially in the area of the unavoidable bends and elbows in the pipes. This heat development further increases the tendency of the powder to bake together, a tendency aggravated by the fact that all customary sprayable powders have a very low melting point. Consequently, it turned out in practice that the powder blown through the pipe lines is inclined to lump, which prevents an even spraying process and may even lead to a complete plugging of the conveying pipes. The lumps developed by the baking together of the heated powder particles become so hard that often it is not possible to unclog the plugged-up lines, consisting in most instances of plastic hose. Moreover, in the case of such an installation it is not. possible to adjust the compressed air to the optimum atomizing conditions, since the jet pump must rather befadjusted at a rate which will convey a fairly usable powder to the spray guns. Another system for the spraying; of powder has bee knownwhere the powder in the supply container is placed in a state of suspension by using compressed air to create a state of turbulence in the container. A revolving textile belt is then dipped into this bed of turbulence. The powder adhering to the belt is then blown from the belt by ventilators toward the object to be coated. Alternatively, a pipe line leading both into and out of the bed of turbulence may be used in this system instead of the revolving textile belt. The pipe line has an opening slit outside the bed of turbulence from which the powder flowing through the pipe line is drawn off in an electrostatic process and is directed toward the workpiece. This system, however, is not well suited for practical use in the case of coating objects moving on an assembly line because neither an exact regulation of the powder dose nor an exact control of the spray jet is possible.

OBJECTS AND SUMMARY OF THE INVENTION The object of the invention is the provision of a process and apparatus preferably for use in an electrostatic compressed air powder spraying system, which guarantees a high degree of effectiveness in measuring the powder dose and minimizes any inclination to breakdowns.

A further object of the invention is to provide a process and apparatus for spraying powder, wherein the powder is kept in a state of turbulence right up'until atomization occurs to prevent thepowder particles from lumping together. I

It is a further object of the invention to provide a powder spraying process and apparatusiwherein an air supply for causing-powder to flow through a spray gun is controlled independently of a turbulence-causing air supply.

It is a still further object of the invention to provide a powder spraying process and apparatus which will prevent powder particles from emerging from the spray gun after the spray guns have been switched off.

It is another object of the invention to provide a process and apparatus which will enable the shape and rate of the flow from a diffuser nozzle to be changed without the powder becoming lumped.

According to the invention, the powder to be atomized is placed in a state of hovering (floating) through the creation of a bed of turbulence, thus making the powder capable of being sprayed. The powder is then taken by the spraying system from the bed of turbulence while maintaining its state of suspension, or hovering.

Although according to the invention the powder is suspended through the formation of a bed of turbulence so it can be sprayed, this suspension need only occur just prior to the point where the powder reaches the actual place of atomization, or diffusion. This results in the essential advantage that for the supplying of the powder from far distant supply containers to the area of atomization, i.e., the spray guns, no special requirements need be set. Therefore, for example, the use of pipes with a large diameter is possible since it is assured that the powder will be in a state capable of being sprayed at the area of atomization.

Because of the direct feeding of the spray guns from the bed of turbulence, it will be possible to measure or monitor the spraying dose precisely and there will be no danger of the spray powder becoming lumped. Moreover, it will result in a high degree of effectiveness since the consumption of air for the formation of a bed of turbulence is comparatively low. Thus, for the actual spraying process only as much compressed air will have to be used as is required for the spraying process.

According to a particularly effective form of the invention, several spraying systems are joined and the spraying systems are controlled independently of one another in regard to shape and direction of the spray jet. The employment of several independently controlled spraying systems results in the essential advantage of a precise adaptation of the spraying installation to the workpieces that are to be coated, whereby the individual spraying systems each withdraw the correct amount of powder, per application, from the common bed of turbulence without the requirement for a control of the conveyance of powder to the spray system.

An apparatus to carry out this process may have, according to the invention, a finishing container to which the pipe line coming from the supply container leads and on which the spray guns have been directly attached. It will be particularly effective to use spray guns such as are shown in German Pat. No. P 16 46 204.7. In this case, the finishing container is shaped as an elongated cylinder, which has at one of its ends a feed opening for the powder, and at the other end a feed opening for the compressed air creating the bed of turbulence. The spray guns may be attached to the pipe jacket of the cylinder provided with suitable openings. The spray guns of the aforementioned patent application are particularly suited for the present purpose, besides their other advantages, since the compressed air required for their operation can be fed in from the side, which considerably facilitates the attachment of the finishing container and the direct sucking off of the powder from the bed of turbulence located in the finishing container.

According to another development of the invention, the spray systems in addition to the diffuser, may have a bell-like body placed on the difiuser, which has been provided with special inlets for the air. In this way it will be possible to widen the spray jet and to change it in regard to its shape as desired.

Other characteristics, advantages and details of the invention will become apparent from the subsequent detailed description in connection with the accompanying drawings which illustrate an example of an embodiment of a device according to the present invention and in which:

THE DRAWINGS FIG. 1 shows a longitudinal section of the finishing container with an attached spray gun;

FIG. 2 shows a longitudinal cut through the axis of the spray gun of FIG. 1 on an enlarged scale;

FIG. 3 is a sectional view of a variation of the spray FIG. 4 shows a longitudinal section of a modified form of the finishing container;

FIG. 5 shows a schematic view of the working arrangement of the apparatus, and

FIG. 6 shows a modified view of a feed pipe.

DETAILED DESCRIPTION In FIG. 1 a finishing container designated by 10 has been shown as a whole in longitudinal section. On the container 10 a single spray gun designated as a whole by 11 has been attached.

The finishing container 10 comprises a generally cylindrical housing pipe 12 which, at the bottom end, is closed by a removable plate 13. At its other open end the container 10 has a feed connection or intake casing 14 for receiving a supply of the powder. At a slight distance from the bottom plate 13, a separating wall 15 made of porous material has been disposed in the housing pipe 12 in such a way that, between the bottom plate 13 and the separating wall 15, an air chamber 16 is defined. Pressurized air can be fed to this chamber 16 through a passage 17 centrally arranged in the plate 13.

In the housing pipe 12 there are provided lateral wall openings 18 spaced at generally equal distances from one another. A spray gun 11 is illustrated as positioned adjacent the lower one of these wall openings 18, while the other wall openings 18 are covered by detachable covers 19.

In FIG. 2, the spray gun 11 is shown in an enlarged scale. This spray gun is also disclosed in the aforementioned German Pat. No. P 16 46 204.7. This gun consists essentially of a driving nozzle 20 and a mixing nozzle 21 placed in front of the driving nozzle. The front end of the mixing nozzle is expanded and functions as a diffuser 21a. Compressed air is fed to the mixing nozzle 21 through a channel 22 formed in collar 22a, which collar surrounds the mixing nozzle.

This spray gun 11 is mounted on a headpiece 23, the latter being attached to a base plate 25 through an intermediate element 24. The base plate 25 is attached to a support plate 26, which in turn is detachably connected to the housing pipe 12 of the finishing container 10. As illustrated, an axial feed channel 27 is provided to communicate the mixing nozzle with the wall opening 18 of the pipe 12, and thus directly with the inside of the finishing container 10. The spray gun 11, together with members 23-26 define a spraying system.

As can be seen in FIG. 2, the headpiece 23 and the intermediate element 24 define a type of ball joint which makes possible a swiveling of the spray gun, in practice for example by 30. Also, the connection of the base plate 25 and the support plate 26 is provided with a suitable swivel, such as that shown at 25a, whereby the base plate can rotate about an axis extending through opening 18.

A pipe insert 28 made of porous material is inserted in the connecting channel 27 in such manner that an annular air chamber 29 is defined by the pipe insert 28 on the one hand and the intermediate element 24, the base plate 25, and the supporting plate 26 on the other hand. A bore 30 is formed in the base plate 25 for supplying compressed air to the air chamber 29.

The method of operation of the device shown in FIGS. l and 2 is as follows. Powdery coating material, such as powdery paints or enamels, is fed from a customary supply container 42 through the feed connection, or intake casing, M to the finishing container Ml. At the same time, compressed air is conducted through the passage opening l7 into the finishing container chamber 116. This compressed air flows through the porous separating wall 15, in an even distribution, into the inside of the housing pipe 12. In this fashion, the powder particles are suspended in a floating state, or fluidized, with a generally even distribution. This floating state can be achieved not only when the housing pipe 12 stands upright, as shown, but also in the case of a horizontal orientation of the housing plate 12. In the latter case, however, the powder should be fed in under pressure.

The spray gun 111 is supplied with compressed air through channel 22. This air will aspirate, or suck, the floating powder particles, located in housing pipe 12, through connecting channel 27 because of the low pressure zone created by the nozzle arrangement such as the one illustrated. The particles are propelled under the effect of the driving nozzle 2d and the mixing nozzle 21, through diffuser 21a in the direction of the object to be coated, which object has not been shown.

A lumping up of the powder particles within the connecting channel 27 is avoided through an important feature of the invention, namely that compressed air is fed through the bore 30 of the air chamber 29. This compressed air will flow at a generally even distribution into channel 27 through the porous pipe insert 28 to create a bed of turbulence within channel 27. The bed of turbulence thus keeps the particles from sticking together in the zone immediately prior to entry into the spray gun.

Therefore it will be assured, according to the invention, that the powdery coating material cannot lump up at any place between the powder intake through the sleeve 14 and the driving nozzle 2% or the mixing nozzle 21. The feeding of the spray gun thus is evenly carried out and the desired dose can be regulated exactly. The overall efficiency is very high since only very small quantities of compressed air are required to produce the bed of turbulence in the housing pipe l2 and in the connecting channel 27. At the same time, the regulation of the compressed air to the spray gun (which air provides particle feeding or aspiration force) can be adjusted in such a way as will seem to be optimum for its method of operation without having to be adjusted to account for feed-in problems such as lumping-up, as in the case of the previously known arrangements.

Another essential advantage of the powder spray device according to the invention consists in the fact that the process of switching-off the system will be improved. It has been determined that by switching-off the air supply to the air chamber 29 (and thus to the connecting channel 27) just shortly prior to switchingoff of the compressed air fed to the gun It through channel 22, individual powder particles will be prevented from further emerging from the spray gun in response to excess pressure in the finishing container or in the feed pipes, even after completion of the spraying process. The reason for this is that immediately after the air supply to the connecting channel 27 is switched-off, something like a closing plug consisting of powder particles will develop in said connecting channel. As such, the pipe insert 28 defining the connecting channel may be considered also as a means defining a plug forming channel.

The plug forming phenomenon is believed to occur since there is no longer turbulence within channel 27 to prevent lumping. Once the air supply is switched back on, however, this process is reversed and the plug or lump becomes fluidified or fluidized. Naturally, in this case one must guard against too extended a time period between switching off the compressed air to the connecting channel 27 and switching off the driving air to the feed channel 22. Otherwise, the closing plug becomes too hard and can no longer be fluidifled upon switching the air back on.

In practice, several spray systems may be attached to the housing pipe 12. For the attachment of additional spray systems it merely is necessary to remove closures l9 and attach in their place additional supporting plates as, each carrying a spray gun. It will be appreciated that a number of possibilities for the arrangement of spray guns ll exists and that it is no problem whatever to replace individual spray guns.

A modified form of the finishing container 10 is shown in FIG. 4% wherein the container is formed of double walls 12 and 15a, spaced from one another to define an air chamber. The inner wall 15a is formed of a porous or foraminous material. Since the air chamber extends over almost the entire inside of the container, a generally uniform distribution of turbulence is created along the length of the container. In the event that such a double-walled container is used, it would be advantageous to provide openings in the inner wall opposite openings 18 of the outer wall with conduits ex tending therebetween. Such a conduit could, for example, constitute an extension 280 of the pipe insert 28.

It may also be effective to provide the finishing cylinder with a conventional metering device, as shown schematically at 40 in FIG. 6, to provide an even degree of filling in the container. It will be apparent that there are numerous types of conventional and commercially available metering devices which could be used. Such a metering device could be connected by wire dtla to any suitable valve 41 in the downpipe 43 to open and close the valve automatically. Such a suitable valve could be one having throttle flaps. I

Finally, the feed connection lld may be provided with a suitable ventilating bore 14a for the purpose of avoiding an excess pressure in container 10. At the same time, it may be effective to extend the feed-connection 14 into the container in the manner of a downpipe 44, as shown in FIG. 6, so that the fluidization process, i.e., the placing of the particles in suspension, will start only at some distance from the intake end of the container.

Generally speaking, in carrying out the invention in a customary spraying compartment, an upright finishing cylinder ltl will be arranged, as shown in FlG. S, on each side of a conveying chain 45 carrying objects to be sprayed. in this manner it will be possible to spray workpieces with a large surface on both sides in one operating step. The finishing cylinders 10 can be provided with a swivel mounting, for example in the form of a ball joint 46 which is fixed to a frame by a rigid rod 47. The containers are thus able to be swiveled, within a certain angle from an upright position, in order to be adjusted for workpieces of various heights. The supplying of the powder to the finishing containers 10 can be accomplished by the use of a single supply container 42 which is disposed above the spraying compartment. This supply container would be in communication with the feed connection 14 on the finishing containers via large diameter feed pipes or downpipes 43.

The invention is preferably intended to be used in an electrostatic compressed air powder spraying system. The setting of the electrostatic field can be accomplished in any customary manner. For example, cables may be connected to the individual spray guns 11 from a high voltage generator located outside the spray com partment in such a way that driving nozzle is connected to a high voltage. Thus, the free lateral edge of diffuser 21a would constitute a charging electrode with respect to powder particles passing therethrough.

A modification of the spray gun 11 according to the present invention is shown in FIG. 3. The spray gun shown in FIG. 3 corresponds basically to that shown in FIGS. 1 and 2 with a change in the construction of the elements comprising the mixing nozzle and the diffuser. As can be seen in FIG. 3, the mixing nozzle 31 expands in the manner of a trumpet into a diffuser 31a. On the diffuser 31a is attached a bell-shaped body 32 in such a way that the diffuser opens into the bell-shaped body. The bell-shaped body 32 defines a mixing chamber. Between diffuser 31a and the bell-shaped body 32, an annular gap 33 is provided. This gap 33 can be fed with compressed air through an annular channel 34 and feed channels 35 in an adjacent collar 35a. Moreover, a number of bores 36 are provided in the wall of the bellshaped body 32, which bores empty tangentially into the inside space of the bell-shaped body. These bores 36 can be supplied with compressed air via an annular channel 37 and a feed channel 38.

The bell-shaped body 32 serves the purpose of broadening the jet of powder emerging from diffuser 31a. Compressed air emerging from the annular gap 33 into the mixing chamber defined by the bell-shaped body 32 will prevent a break in the powder flow at the lateral edge of diffuser 31a. The compressed air emerging from the tangential bores 36 will transfer a rotational movement to the powder to prevent an adherence of powder to the inside surface of the bellshaped body.

By a suitable mutual adjustment of the amounts of compressed air fed to the inlet channels 22, 35, and 38, the force and the shape of the jet of powder can be varied within wide limits. This is of importance particularly in the case of the use of a group of spray guns, wherein each spray gun can be adjusted independently. For example, it might be desirable in order to achieve an even coating to operate highenpositioned spray guns differently from lower-positioned guns, in order to equalize the effect of gravity. In this form of the invention, the electric high voltage is applied to the bellshaped body 32, the lateral edge of which then serves as an electrode for the powder particles.

It is again noted that this independent control of a group of spray guns connected with a single tank is made possible by the bed of turbulence according to the invention, since each spraying gun can suck ofi its own required quantity of powder in each instance.

SUMMARY OF ADVANTAGES OF INVENTION The present invention, by providing the container 10 and channel 27 with a supply of compressed air through openings 17 and 30, respectively, ensures that the powder particles therein are kept in a state of relatively uniform suspension, thus preventing them from lumping together and clogging the system.

Moreover, since the fiow of suspension-causing compressed air is controlled independently of the suctioncausing compressed air flow, the rate of the latter can be determined solely with regard to delivering the proper powder dosage, and not with regard to preventing lumping-up of the particles.

A related advantage of keeping the particles in a state of suspension is that the suction pressure, caused by compressed air passingthrough opening 22 and mixing nozzle 21, will enable particles to be aspirated from chamber 10 at a relatively uniform rate, permitting the powder dosage to be precisely regulated.

Furthermore, by cutting off the supply of compressed air to opening 30, just before cutting off the compressed air feed to the gun 11, the particles located in pipe insert 28 lump together. This restricts the undesired flow of powder through pipe insert 28, responsive to residual pressure in container 10, when the spray gun 11 is switched off.

Additionally, the provision on the diffuser of a bellshaped body 32 having channels 33 and 35 for the passage of compressed air enables the force and shape of the powder flow to be changed. More specifically, air passing through channel 33 prevents the flow at the lateral edge of the diffuser from breaking up, while tangential inlets 36 prevent powder from adhering to the bell-shaped body.

Certain modifications have been described as contemplated within the scope of the present invention. Included in these are the following: The finishing container 10 may be formed of double walls, the inner of which being porous to create a uniform turbulence throughout the entire chamber; a meter may be provided to automatically regulate the amount of powder within the finishing container; the feed connection 14 may be provided with a ventilating bore to relieve excess pressure in the finishing container; the feed con nection 14 may also be extended within the finishing container to cause the fluidization of the particles to be limited to a distance from the container intake; the finishing container may be mounted on a swivel so as to be pivotal from its upright position, thus varying the height of the spray guns.

Although the invention has been described with reference to particular preferred forms, it will be appreciated by those skilled in the art that additions, substitutions, modifications, and deletions not specifically described may be made without departing from the spirit or scope of the present invention as defined in the appended claims.

What is claimed is:

1. A process for coating objects with powdery substances, the process utilizing: a finishing container; at least one compressed air operated spraying system, including a powder diffusing means, being connected to and communicating with the finishing container; first means for creating a bed of turbulence within the finishing container; means for creating a bed of turbulence within the spraying system adjacent the diffusing means; and third means, cooperable with said diffusing means, for creating an aspirating force to aspirate powder particles from the finishing container through the diffusing means; the process comprising:

creating a first bed of turbulence in the finishing container to place powder particles contained therein in a fluidized state;

creating a second bed of turbulence within the spraying system adjacent the diffusingmeans to place powder particles located thereat in a fluidized state; and

aspirating powder particles from the finishing container through the diffusing means while maintaining the particles in a fluidized state.

2. The process of claim ll further utilizing: a plurality of spraying systems connected to the finishing container; and means for independently controlling the flow output of each spraying system; the process further including the step of:

independently controlling the flow output of each spraying system.

3. Apparatus for coating objects with powdery substances and comprising:

a finishing container;

at least one compressed air operated spraying system, including a powder diffusing means, being connected to and communicating with the finishing container;

first means for creating a bed of turbulence within the finishing container to place powder particles located therein in a fluidized state;

second means for creating a bed of turbulence within the spraying system adjacent the diffusing means to place powder particles located thereat in a fluidized state; and

third means, cooperable with the diffusing means, for creating an aspirating force to aspirate powder particles from the finishing container through the diffusing means; the beds of turbulence in the diffusing means and in the spraying system being operable to maintain the particles in a fluidized state during movement of the particles to the diffusing means.

4. Apparatus according to claim 3 wherein the finishing container comprises:

a generally upright cylinder, on the outer surface of which is mounted at least one spraying system; and

the cylinder having a feed connection at its upper end adapted for communication with a powder supply container;

the lower end of the cylinder being defined by a bottom plate in which is provided an opening adapted to receivecompressed air.

5. Apparatus according to claim 4 wherein the cylinder further includes:

a wall of porous material spaced from the bottom plate and defining therewith an air chamber;

the opening being positioned at the lower end of the chamber.

6. Apparatus according to claim 3 wherein the finishing container comprises:

a generally upright cylinder formed of inner and outer spaced-apart walls defining an air chamber therebetween;

the inner wall being formed of a porous material;

the outer wall being connected to means adapted to supply compressed air into the airchamber.

7. Apparatus according to claim 4 wherein the feed connection includes a continuous bore to provide ven tilation for the cylinder.

8. Apparatus according to claim 4 wherein the feed connection includes a conduit extending downwardly into the cylinder interior.

9. Apparatus according to claim 4 further including:

regulating means for automatically controlling the amount of powder within the cylinder.

10. Apparatus according to claim 4 wherein the cylinder further includes:

a plurality of openings, each being adapted for communication with a spraying system; and

a cover detachably positioned over each opening being in non-communication with a spraying system.

11. Apparatus according to claim 10 wherein the spraying system is swivelly mounted on the cylinder to permit the spraying system to rotate about its longitudinal axis with respect to the cylinder.

12. Apparatus according to claim 11 .wherein the spraying system includes a universal swivel connection permitting the diffusing means to pivot with respect to the cylinder.

13. Apparatus according to claim 12 wherein the spraying system further includes:

a supporting foot having a channel communicating with the diffusing means; and

a porous pipe member being positioned within inner walls of the channel and spaced therefrom to define an air chamber;

the chamber being connected to a source of compressed air.

14. Apparatus according to claim 4 wherein the cylinder is. swivelly mounted so as to be pivotal from an upright position to an angled position.

15. Apparatus according to claim 4 and further including an additional finishing container positioned opposite the first-mentioned finishing container;

a powder supply container mounted above the finishing containers; and

powder guide means connected between the supply container and each finishing container.

16. Apparatus according to claim 4 wherein the diffusing means includes:

a longitudinally extending diffuser member;

a generally bell-shaped body positioned on the outer end of the diffuser member and having at least one opening therein; and

a supply line being connected between the opening and a source of compressed air.

17. Apparatus according to claim 16 wherein:

the bell-shaped body has an inside wall spaced from the outer end of the diffuser member to define the opening.

18. Apparatus according to claim 16 and further including:

a plurality of bores being formed in the bell-shaped body and being directed inwardly of the bellshaped body; and

feed channel means being connected to the bores and connected to a source of compressed air.

19. Apparatus according to claim 4 wherein the first and second means for creating a bed of turbulent flow in the finishing container and spraying system, respectively, and the means for creating an aspirating force each includes an independently controlled flow of compressed air.

20. Apparatus according to claim 4 and further including:

a powder supply container, and

a guiding conduit extending between the powder supply container and the finishing container.

21. In a spraying apparatus having a longitudinally extending diffuser member, the combination therewith of a spray attachment comprising:

a generally bell-shaped body positioned on the outer end of the diffuser member;

the generally bell-shaped body having an inner wall spaced from the diffuser means to define therewith an annular gap; and

a supply line being connected between the annular gap and a source of compressed air.

22. A method of preventing ejection of powder particles from a powder spraying system, the method utilizing: a longitudinally extending diffuser member; first means cooperating with the diffuser member for creating an aspirating force therein and adapted to draw powder particles through the diffuser member from a powder source positioned away from the diffuser member; a channel-forming member connected to the diffuser member and adapted to communicate the diffuser member with the powder source; and second means for optionally creating a bed of turbulence within the channel forming member to prevent powder particles located therein from lumping together; the method comprising:

rendering the second means incapable of creating a bed ofturbulence just prior to rendering the first means incapable of creating an aspirating force, to cause the powder particles located in the channel forming member to lump together for preventing a flow of powder to the diffuser member.

23. A powder spraying system comprising:

a longitudinally extending diffuser member;

first means cooperable with the diffuser member for creating an aspirating force therein and adapted to draw powder particles through the diffuser member from a remotely-positioned powder source;

a channel-forming member connected to the diffuser member and adapted to communicate the diffuser member with the powder source;

second means, including a foraminous pipe positioned in the channel-forming member, for optionally creating a bed of turbulence within the channel-forming member to prevent powder particles located therein from lumping together; and means for rendering the second means inoperable prior to rendering the first means inoperable, for permitting the powder particles located within the channel-forming member to lump together to close-off communication with the diffuser member. 

1. A process for coating objects with powdery substances, the process utilizing: a finishing container; at least one compressed air operated spraying system, including a powder diffusing means, being connected to and communicating with the finishing container; first means for creating a bed of turbulence within the finishing container; means for creating a bed of turbulence within the spraying system adjacent the diffusing means; and third means, cooperable with said diffusing means, for creating an aspirating force to aspirate powder particles from the finishing container through the diffusing means; the process comprising: creating a first bed of turbulence in the finishing container to place powder particles contained therein in a fluidized state; creating a second bed of turbulence within the spraying system adjacent the diffusing means to place powder particles located thereat in a fluidized state; and aspirating powder particles from the finishing container through the diffusing means while maintaining the particles in a fluidized state.
 2. The process of claim 1 further utilizing: a plurality of spraying systems connected to the finishing container; and means for independently controlling the flow output of each spraying system; the process further including the step of: independently controlling the flow output of each spraying system.
 3. Apparatus for coating objects with powdery substances and comprising: a finishing container; at least one compressed air operated spraying system, including a powder diffusing means, being connected to and communicating with the finishing container; first means for creating a bed of turbulence within the finishing container to place powder particles located therein in a fluidized state; second means for creating a bed of turbulence within the spraying system adjacent the diffusing means to place powder particles located thereat in a fluidized state; and third means, cooperable with the diffusing means, for creating an aspirating force to aspirate powder particles from the finishing container through the diffusing means; the beds of turbulence in the diffusing means and in the spraying system being operable to maintain the particles in a fluidized state during movement of the particles to the diffusing means.
 4. Apparatus according to claim 3 wherein the finishing container comprises: a generally upright cylinder, on the outer surface of which is mounted at least one spraying system; and the cylinder having a feed connection at its upper end adapted for communication with a powder supply container; the lower end of the cylinder being defined by a bottom plate in which is provided an opening adapted to receive compressed air.
 5. Apparatus according to claim 4 wherein the cylinder further includes: a wall of porous material spaced from the bottom plate and defining therewith an air chamber; the opening being positioned at the lower end of the chamber.
 6. Apparatus according to claim 3 wherein the finishing container comprises: a generally upright cylinder formed of inner and outer spaced-apart walls defining an air chamber therebetween; the inner wall being formed of a porous material; the outer wall being connected to means adapted to supply compressed air into the air chamber.
 7. Apparatus according to claim 4 wherein the feed connection includes a continuous bore to provide ventilation for the cylinder.
 8. Apparatus according to claim 4 wherein the feed connection includes a conduit extending downwardly into the cylinder interior.
 9. Apparatus according to claim 4 further including: regulating means for automatically controlling the amount of powder within the cylinder.
 10. Apparatus according to claim 4 wherein the cylinder further includes: a plurality of openings, each being adapted for communication with a spraying system; and a cover detachably positioned over each opening being in non-communication with a spraying system.
 11. Apparatus according to claim 10 wherein the spraying system is swivelly mounted on the cylinder to permit the spraying system to rotate about its longitudinal axis with respect to the cylinder.
 12. Apparatus according to claim 11 wherein the spraying system includes a universal swivel connection permitting the diffusing means to pivot with respect to the cylinder.
 13. Apparatus according to claim 12 wherein the spraying system further includes: a supporting foot having a channel communicating with the diffusing means; and a porous pipe member being positioned within inner walls of the channel and spaced therefrom to define an air chamber; the chamber being connected to a source of compressed air.
 14. Apparatus according to claim 4 wherein the cylinder is swivelly mounted so as to be pivotal from an upright position to an angled position.
 15. Apparatus according to claim 4 and further including an additional finishing container positioned opposite the first-mentioned finishing container; a powder supply container mounted above the finishing containers; and powder guide means connected between the supply container and each finishing container.
 16. Apparatus according to claim 4 wherein the diffusing means includes: a longitudinally extending diffuser member; a generally bell-shaped body positioned on the outer end of the diffuser member and having at least one opening therein; and a supply line being connected between the opening and a source of compressed air.
 17. Apparatus according to claim 16 wherein: the bell-shaped body has an inside wall spaced from the outer end of the diffuser member to define the opening.
 18. Apparatus according to claim 16 and further including: a plurality of bores being formed in the bell-shaped body and being directed inwardly of the bell-shaped body; and feed channel means being connected to the bores and connected to a source of compressed air.
 19. Apparatus according to claim 4 wherein the first and second means for creating a bed of turbulent flow in the finishing container and spraying system, respectively, and the means for creating an aspirating force each includes an independently controlled flow of compressed air.
 20. Apparatus according to claim 4 and further including: a powder supply container, and a guiding conduit extending between the powder supply container and the finishing container.
 21. In a spraying apparatus having a longitudinally extending diffuser member, the combination therewith of a spray attachment comprising: a generally bell-shaped body positioned on the outer end of the diffuser member; the generally bell-shaped body having an inner wall spaced from the diffuser means to define therewith an annular gap; and a supply line being connected between the annular gap and a source of compressed air.
 22. A method of preventing ejection of powder particles from a powder spraying system, the method utilizing: a longitudinally extending diffuser member; first means cooperating with the diffuser member for creating an aspirating force therein and adapted to draw powder particles through the diffuser member from a powder source positioned away from the diffuser member; a channel-forming member connected to the diffuser member and adapted to communicate the diffuser member with the powder source; and second means for optionally creating a bed of turbulence within the channel forming member to prevent powder particles located therein from lumping together; the method comprising: rendering the second means incapable of creating a bed of turbulence juSt prior to rendering the first means incapable of creating an aspirating force, to cause the powder particles located in the channel forming member to lump together for preventing a flow of powder to the diffuser member.
 23. A powder spraying system comprising: a longitudinally extending diffuser member; first means cooperable with the diffuser member for creating an aspirating force therein and adapted to draw powder particles through the diffuser member from a remotely-positioned powder source; a channel-forming member connected to the diffuser member and adapted to communicate the diffuser member with the powder source; second means, including a foraminous pipe positioned in the channel-forming member, for optionally creating a bed of turbulence within the channel-forming member to prevent powder particles located therein from lumping together; and means for rendering the second means inoperable prior to rendering the first means inoperable, for permitting the powder particles located within the channel-forming member to lump together to close-off communication with the diffuser member. 